Magnetic stirrers have been known for many years. Typically, in these known magnetic stirrers, a magnetic stirring bar is placed in a container of liquid. By rotating a permanent magnet below the container, a rotating magnetic field is produced which, in turn, causes the magnetic stirring bar to rotate within the container, thereby stirring the contents thereof. These magnetic stirrers are especially useful to maintain the suspension of a reagent, such as a protein suspension, which is to undergo coagulation testing (see, for instance, U.S. Pat. Nos. 3,754,866 and 3,650,698).
Generally, the effectiveness of any mixing technique is directly proportional to the amount of turbulence created thereby. In the known magnetic stirrers described above, the turbulence in the liquid to be mixed is created primarily by a simple rotational movement of the stirring bar. Because the rotation of the stirring bar is relatively constant and uniform, a vortex is formed in the liquid being mixed. The creation of a vortex is disadvantageous because it limits the amount of turbulence that can be created in the liquid and tends to pull heavier particles to the bottom of the container.